Heat exchanger and heating or air conditioning unit of a motor vehicle containing said heat exchanger

ABSTRACT

The invention relates to a heat exchanger of a plate-type construction having first flow channels for a first heat exchange medium, each formed by a pair of plates, and having corrugated fins, around which a second heat exchange medium flows, arranged between neighboring plate pairs. In order to provide an improved heat exchanger which allows a more compact construction when used in a heating or air conditioning unit of a motor vehicle, it is proposed that the corrugated fins and at least one of the neighboring plate pairs form second flow channels for the second heat exchange medium and the second flow channels have a curved course, so that the second heat exchange medium undergoes a change of flow direction on flowing through the heat exchanger.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a heat exchanger of a plate-typeconstruction, and a heating or air conditioning unit for a motor vehicleequipped therewith.

[0002] An air conditioning unit as disclosed, for example, in DE 198 04389 has an evaporator of what is referred to as a plate-typeconstruction. The evaporator has first flow channels, each formed from apair of plates, for a coolant of the air conditioning unit, andcorrugated fins, around which the air to be cooled flows, arranged ineach case between neighboring plate pairs. Such known plate-typeevaporators, as they are called, are of cuboid construction and are usedin the air conditioning unit between a fan and a heater to cool the airto be passed into the passenger compartment.

[0003] Motor vehicles today are intended to be as compact as possible intheir external dimensions, the interior space being as large aspossible. Accordingly, efforts are made to design increasingly compactair conditioning units, so that they take up as little structural spaceas possible. Designers therefore attempt to make the individualcomponents of the air conditioning unit smaller and more efficient, asshown, for example, by DE 197 19 252, in which the evaporator describedis designed such that its overall depth is no more than 50 mm.

SUMMARY OF THE INVENTION

[0004] It is an object of the invention to provide an improved heatexchanger and a heating or air conditioning unit equipped therewithwhich has a reduced structural volume.

[0005] It is also an object of the invention to provide an improvedmethod of assembling a heat exchanger assembly that includes plural heatexchangers.

[0006] In accomplishing the objects of the invention, there has beenprovided in accordance with one aspect of the invention a plate-typeheat exchanger comprising: a plurality of stacked plates, withrespective adjacent plates forming pairs of plates, the plates of thepairs being joined together to define a plurality of first flow channelstherebetween for carrying a first heat exchange medium; and finsarranged between neighboring pairs of said plates, said fins and atleast one of said neighboring pairs of plates forming a plurality ofsecond flow channels for carrying a second heat exchange medium, whereinsaid fins are shaped such that the second heat exchange medium has ageneral flow direction in said second flow channels that is changed asit flows through the heat exchanger.

[0007] In accordance with another aspect of the invention, there hasbeen provided a heating or air conditioning unit comprising: a firstplate-type heat exchanger; and a second plate-type heat exchanger,wherein one or both of said first and second plate-type heat exchangerscomprises: a plurality of stacked plates, with respective adjacentplates forming pairs of plates, the plates of the pairs being joinedtogether to define a plurality of first flow channels therebetween forcarrying a first heat exchange medium; and fins arranged betweenneighboring pairs of said plates, said fins and at least one of saidneighboring pairs of plates forming a plurality of second flow channelsfor carrying a second heat exchange medium, wherein said fins are shapedsuch that the second heat exchange medium has a general flow directionin said second flow channels that is changed as it flows through eachrespective heat exchanger.

[0008] According to still another aspect of the invention, there hasbeen provided a method for assembling a heat exchange assembly comprisedof a first plate-type heat exchanger; and a second plate-type heatexchanger, wherein each of said first and second plate-type heatexchangers comprises: a plurality of stacked plates, with respectiveadjacent plates forming pairs of plates, the plates of the pairs beingjoined together to define a plurality of first flow channelstherebetween for carrying a first heat exchange medium; and finsarranged between neighboring pairs of said plates, said fins and atleast one of said neighboring pairs of plates forming a plurality ofsecond flow channels for carrying a second heat exchange medium, whereinsaid fins are shaped such that the second heat exchange medium has ageneral flow direction in said second flow channels that is changed asit flows through each respective heat exchanger, comprising: assemblinga stack of said plates for said first heat exchanger in alignment withone another and a stack of said plates for said second heat exchanger inalignment with each other, wherein at least some of the plates of saidfirst heat exchanger are connected to corresponding plates of saidsecond heat exchanger; during said stack assembling, interposing saidfins between each neighboring pair of plates for forming said secondflow channels; and brazing each of said pair of plates together on atleast their outer circumference to form said first flow channels andbrazing said fins to adjacent pairs of plates to form said second flowchannels, whereby said first and second heat exchangers are produced ina single assembly operation.

[0009] Further objects, features and advantages of the present inventionwill become apparent from the detailed description of preferredembodiments that follows, when considered together with the accompanyingfigures of drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The invention is explained in detail below with reference toexemplary embodiments, and with reference to the accompanying drawings,in which:

[0011]FIG. 1 shows a perspective view of a heat exchanger according tothe invention;

[0012]FIG. 2 shows a pair of plates with a neighboring corrugated fin;

[0013]FIG. 2a shows a partial cross section in the edge region of theheat exchanger according to the invention;

[0014]FIG. 3 shows a plan view of a plate;

[0015]FIG. 4 shows a plate with a neighboring corrugated fin of a systemconsisting of two heat exchangers;

[0016]FIG. 5 shows a plate with a corrugated fin corresponding to FIG. 4of another embodiment;

[0017]FIG. 6 shows an air conditioning unit according to the inventionhaving a heat exchanger according to the invention as an evaporator;

[0018]FIG. 7 shows an air conditioning unit according to the inventionwith an evaporator and heater designed according to the invention;

[0019]FIG. 8 shows a further embodiment of an air conditioning unitaccording to the invention with temperature control on the air side; and

[0020]FIG. 9 shows an air conditioning unit according to the inventionwith temperature control on the water or coolant side.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0021] According to the invention, the corrugated fins and at least oneof the neighboring plate pairs form second flow channels for a secondheat exchange medium, for example, for air, which flows through the heatexchanger, the second flow channels having a curved course, so that thesecond heat exchange medium undergoes a change of flow direction onflowing through the heat exchanger. With such a heat exchanger, which nolonger has to be of cuboid construction and through which the air doesnot flow in a linear manner, the air need not, as previously in knownair conditioning units, be deflected upstream and downstream of the heatexchanger. Instead, the air is deflected directly in the heat exchangeras it flows through. The heat exchanger performs both the function ofcooling or heating the air flowing through, depending on the intendedpurpose, and the function of guiding the air. As a result, at least to acertain extent, air deflections on the air side is upstream and/ordownstream of the heat exchanger can be dispensed with, and the heatingor air conditioning unit, or the air guide housing of that unit, can beof more compact design.

[0022] Advantageous embodiments of the invention are described herein.

[0023] When the air undergoes a change of direction in the heatexchanger, an air inflow face and an air exit face of the heat exchangerare non-parallel and are advantageously arranged at an angle α to oneanother. The angle α depends on the degree to which it is desired tochange the direction of air flow in each application. Typically, theangle α is greater than 30° and less than 150°, more typically from 60°to 120°. For many applications, the angle α is preferably approximately90°.

[0024] In one embodiment of the invention, the individual second flowchannels are of different lengths, and it is particularly advantageousif the second flow channels become longer with increasing distances froma feed for the first heat exchange medium, so that in the vicinity ofthe feed, where a relatively large temperature difference exists betweenthe two media, the second flow channels are relatively short andtherefore the heat exchange only needs to take place over a shorterpath. At a greater distance from the feed, the temperature differencebetween the two media becomes smaller and therefore the flow channelsare advantageously longer, so that the air, which is guided in the heatexchanger independently of the position of the second flow channel intoa particular flow channel, is always brought to the same temperaturelevel.

[0025] Advantageously, for flow purposes, the second flow channelspreferably have an arcuate course, especially a circular arcuate course.As a result, pressure losses for the air are reduced, despitedeflection.

[0026] The first flow channels preferably have a serpentine course inorder to optimize heat exchange with the second heat exchange medium.

[0027] In a structurally simple manner, the corrugated fins may bepunched from sheet metal.

[0028] If two heat exchangers are to be used, for example an evaporatorand a heater in an air conditioning unit, and the two heat exchangersare connected in series on the air side, it is advantageous if both heatexchangers are designed according to the invention and the is plates ofthe two heat exchangers are integrally connected to one another. Thenthe two heat exchangers can be produced simultaneously in a singleproduction process by jointly arranging in series and brazing the platesand corrugated fins. In the further assembly of the air conditioningunit, also, advantages are achieved in that the heat exchangers can besimultaneously inserted as one unit into the air conditioning unit.Overall, this can save numerous assembly steps.

[0029] In order nevertheless to decouple the two heat exchangersthermally as far as possible, it is advantageous if the plates of theheat exchangers are connected to one another only in the region of theirpassage apertures, which in each case form collection spaces for thefirst heat exchange medium. As a result, a further advantage is alsoachieved that water of condensation forming in the heat exchanger whichis used as an evaporator can run off better between the heat exchangers.

[0030] Particularly advantageously, the heat exchanger according to theinvention can be used in a heating or air conditioning unit as anevaporator and/or heater, since structural space can thus be saved inthe manner already described. In this case, the air conditioning unitcan either be adjustable on the coolant side, e.g., by having the flowof the first heat exchange medium through the heater be adjustable, orthe heating or air conditioning unit can be adjusted on the air side, inwhich case a heater bypass is provided on the air side. In an airconditioning unit which has an evaporator and/or heater of the structureaccording to the invention, the air is deflected less frequently andwith a reduced pressure loss, and there is reduced disruption to theairflow. By adjustment on the air side, the separation of the partialstreams of air downstream of the heater will be relatively great. Thismeans that there is less mixing of cold and warm air and the temperaturedifferences over the cross section of the airflow downstream of theheater are relatively great. This can be exploited in a desirable mannerto pass warmer air to a foot space and a windshield and the colder airto outlets in the central plane of the vehicle.

[0031] A very compact heating or air conditioning unit is obtained ifthe heat exchanger or heat exchangers each divert the air throughapproximately 90°.

[0032] Turning now to the drawings, a heat exchanger 10 according to theinvention, as shown in the figures, has first and second plates 12 and14, which in each case form a plate pair 16 and are connected, forexample, brazed, to one another at least at the edges and thereby formfirst flow channels 18 between them in each case for a first heatexchange medium (FIG. 2a). Corrugated fins 20 are arranged in each casebetween two neighboring plate pairs 16. The corrugated fins 20 areconnected, especially brazed, to their neighboring plate pairs 16, sothat the corrugated fins 20 and at least one of the neighboring platepairs 16 form second flow channels 22 for a second heat exchange medium.In the embodiment shown, the second flow channels have a rectangularcross section because of the shape of the corrugated fin 20. Othershapes are conceivable, such as depending on the form of corrugation ofthe corrugated fin 20. When the first heat exchange medium flows throughthe heat exchanger via the first flow channels and the second heatexchange medium via the second flow channels, heat exchange takes placebetween the media.

[0033] The plates 12 and 14 have approximately the shape of aquarter-circle and have two passage apertures 26 and 28 at an end 24facing a center of the circle, each passage aperture 26 and 28 having acollar, 30 and 32 respectively, so that in the assembled state of theheat exchanger the collars of neighboring plate pairs can be connected,especially brazed, to one another so that the mutually flush passageapertures 26 and 28 in each case form a collection space for the firstheat exchange medium. The first heat exchange medium is fed to orremoved from the heat exchanger via a feed 34 or outlet 36.

[0034] The first flow channels 18 are open toward the inlet apertures 26and outlet apertures 28, so that the first heat exchange medium can flowin from the feed 34 and thus through the passage apertures 26 into allflow channels 18 in parallel and can flow from the flow channels 18 intothe passage apertures 28 and to the outlet 36. Within a plate pair 16,the flow channel 18 has a serpentine course, which is produced by webs40, 42, 44 extending radially from the passage apertures (FIG. 3). Theserpentine flow course of the first heat exchange medium is indicated bythe arrows 46 in FIG. 3. In order to enable the flow channels 18 formedby the plates 12 and 14 to have a more pressure-stable design, knobs orprotrusions 13 are additionally provided, as required, these being shownonly in one sub-area in FIG. 3. The knobs 13 of the plates 12 and 14 arearranged opposite one another in pairs (FIG. 2) and brazed to oneanother, and they prevent the plates 12 and 14 from bending away ortoward one another.

[0035] The second heat exchange medium, which in preferred intended usesof the invention is air, flows through the second flow channels 22.Channels 22 have a curved course, especially a circular arcuate course,in accordance with the shape of the plate pairs 16 and corrugated fins20, so that each flow channel 22 describes a quarter-arc, the flowchannels 22 having different lengths and the flow channels 22 becominglonger as the radial distance from the passage apertures 26 and 28respectively becomes greater (FIG. 2).

[0036] The heat exchanger 10 according to the invention, in whose secondflow channels the second heat exchange medium undergoes a change of flowdirection, has an inflow face 50 for the second heat exchange medium,arranged at an angle a of preferably approximately 90° to an exit face52 for the second heat exchange medium, as is shown in FIG. 1, in whichthe airflow is represented by arrows 53 and 54. If the flow direction ofthe second heat exchange medium is to be changed by more or less than90° in any given application, the angle a may have a correspondinglydifferent value.

[0037] If two heat exchangers according to the invention are to bearranged in series in the flow direction of the second heat exchangemedium, the individual plates 12 and 14 may be connected to one another,as is shown in the embodiments according to FIGS. 4 and 5. The firstflow channels of the first heat exchanger 10 should not be in fluidconnection with the first flow channels of the second heat exchanger10′. In principle, the second flow channels 22 of the first heatexchanger 10 may be integral with the second flow channels 22′ of thesecond heat exchanger 10′, the corrugated fin 20 being continuous andconsisting of a single piece for the two heat exchangers 10 and 10′.However, it is advantageous for purposes of thermal decoupling for thecorrugated fin to be separated into two corrugated fins 20 and 20′ forthe heat exchanger 10 and for the heat exchanger 10′, as shown in FIG.4. Further thermal decoupling may be achieved if the plates 12 and 14are connected only in the region of the passage apertures 26 and 28 or26′ and 28′, respectively, as shown in FIG. 5.

[0038] The heat exchanger 10 according to the invention is preferablyused in heating or air conditioning units. FIG. 6 illustrates anexemplary embodiment, in which the heat exchanger is used as anevaporator 102. Air to be conditioned is directly fed by a radial fan104 (not shown in detail) to the inflow face 106 of the evaporator 102.In the evaporator 102, the air is cooled and simultaneously deflected inthe direction of an air mixing space 108, in which the air cooled in theevaporator 102 can be mixed with air warmed in a heater 110 of aconventional type. Via a mixing valve 112, part of the cold air emergingfrom the exit face 114 of the evaporator 102 can be removed toward theheater 110 and, via a warm air channel 116, passed to the air mixingspace 108 as warm air. From the air mixing space 108, some of the air ispassed via a defrosting air channel 118 and a defrosting air valve 120to the windshield. Via a foot space air channel 122 and a foot space airvalve 124, air can be fed to a foot space. An air channel for guidingair to outlets in a central plane of the passenger compartment is notspecifically shown in FIG. 6, but is generally present.

[0039] The hatched surface 130 shown above the fan 104 in FIG. 6represents the space that can be saved by using the heat exchanger 102according to the invention instead of a conventional cuboid evaporator.

[0040] The structural volume of the heating or air conditioning unitaccording to the invention can be further reduced if, as shown in FIG.7, the heater is also designed according to the invention and thus ablenot only to warm the air but also to deflect it.

[0041] A further substantial reduction in structural volume is obtainedif both the evaporator 102 and the heater 110′ are designed according tothe invention, and thus not only condition the air but can also deflectit and, at the same time, are arranged in series on the airflow side, asshown in the exemplary embodiment according to FIG. 8. The evaporator102 is installed directly downstream of the fan 104, and the heater 110′is again fitted downstream of the evaporator 102, the inflow face 140 ofthe heater 110′ being aligned approximately parallel to the air exitface 114 of the evaporator 102. The second flow channels of theevaporator 102 and of the heater 110′, having a circular arcuate shape,then extend in such a way that the centers of the circles of thecircular arcuate courses are located at least approximately in the samevicinity. In this embodiment, air is passed from the outlet 150 of thefan 104 to the air mixing space 108 on a circular arcuate path anduniformly deflected by only 180° and in a manner favoring flow, as aresult of which smaller pressure losses are achieved.

[0042] A mixing valve 112 is arranged between the air inflow face 140and the air exit face 115 114, and adjusts the quantity of air passed tothe heater 110′. Pneumatically parallel to the heater 110′ on theairflow side is a heater bypass 142, which can be closed via a bypassvalve 144. Thus, cold air cooled in the evaporator can be guided pastthe heater and passed to the air mixing space 108. The warm air emergingat the air exit face 146 of the heater 110′ likewise enters the airmixing space and can mix with the cold air present there. Branching offfrom the air mixing space 108 are the defrosting air channel 118, thefoot space air channel 122 and an air channel 148 which leads to outletsin the central plane of the vehicle. The air channels branching off fromthe air mixing space 108 can in each case be shut off by means of airvalves.

[0043] In a further embodiment of the invention, shown in FIG. 9, theevaporator 102 and the heater 110′ are again both designed in accordancewith the invention. In this case, the heater 110′ and the evaporator 102are arranged in series on the air side without an interposed air flap.All the air initially flows through the evaporator 102 and is cooledthere, and then through the heater 110′, where it is reheated asnecessary. To regulate the air temperature, the flow of the first heatexchange medium through the heater 110′ is adjustable. This first heatexchange medium is generally the coolant of the internal combustionengine of the motor vehicle. In this embodiment of the heating or airconditioning unit according to the invention, the system has two heatexchangers designed as shown in FIGS. 4 and 5. These heat exchangersconnected to one another and produced in a single production process,which was described earlier, and can be used with particular advantage.In this case, again, the second flow channels of the evaporator 102 andof the heater 110′, having a circular arcuate shape, extend in such away that the centers of the circles represented by the circular arcuatecourses are located at least approximately in the same vicinity. In thiscase, again, the air is uniformly deflected by only 180° from the outletof the radial fan 104 to the space 108′ downstream of the heater 110′ onthe airflow side. From the space 108′, the conditioned air is passed ina known manner via air valves and the individual air channels to thepassenger compartment.

[0044] The disclosure of German priority patent application number DE100 10 266.2, filed Mar. 2, 2000, is hereby incorporated by reference inits entirety.

[0045] The foregoing embodiments have been shown for illustrativepurposes only and are not intended to limit the scope of the invention,which is defined by the claims.

We claim:
 1. A plate-type heat exchanger comprising: a plurality ofstacked plates, with respective adjacent plates forming pairs of plates,the plates of the pairs being joined together to define a plurality offirst flow channels therebetween for carrying a first heat exchangemedium; and fins arranged between neighboring pairs of said plates, saidfins and at least one of said neighboring pairs of plates forming aplurality of second flow channels for carrying a second heat exchangemedium; wherein said fins are shaped such that the second heat exchangemedium has a general flow direction in said second flow channels that ischanged as it flows through the heat exchanger.
 2. A heat exchangeraccording to claim 1 , wherein said fins comprise corrugated fins.
 3. Aheat exchanger according to claim 2 , wherein said second flow channelshave a curved course for heat exchange medium flow.
 4. A heat exchangeraccording to claim 3 , further comprising: an inflow face for saidsecond heat exchange medium; and an exit face for said second heatexchange medium, wherein said inflow face and said exit face arearranged at an angle to one another.
 5. A heat exchanger according toclaim 3 , wherein said second heat exchange medium comprises air.
 6. Aheat exchanger according to claim 5 , further comprising: an inflow facefor said second heat exchange medium; and an exit face for said secondheat exchange medium, wherein said inflow face and said exit face arearranged at an angle to one another.
 7. A heat exchanger of claim 3 ,wherein at least two of said second flow channels have differentlengths.
 8. A heat exchanger of claim 7 , wherein said second flowchannels include flow channels of shorter length and flow channels oflonger length, and wherein the shorter second flow channels are locatedin an area of the heat exchanger in which the first heat exchange mediumis at a warmer temperature than its temperature when in the area of theheat exchanger where the longer second flow channels are located.
 9. Aheat exchanger of claim 7 , further comprising: at least one passageaperture for the first heat exchange medium, wherein each of said secondflow channels is of increasing length with increasing distance from saidpassage aperture.
 10. A heat exchanger of claim 4 , wherein said secondflow channels have an arcuate course for heat exchange medium flow. 11.A heat exchanger of claim 9 , wherein said second flow channels have anarcuate course for heat exchange medium flow.
 12. A heat exchanger ofclaim 10 , wherein said second flow channels have a circular arcuatecourse for heat exchange medium flow.
 13. A heat exchanger of claim 11 ,wherein said second flow channels have a circular arcuate course forheat exchange medium flow.
 14. A heat exchanger of claim 3 , whereinsaid first flow channels have a serpentine course for heat exchangemedium flow.
 15. A heat exchanger of claim 9 , wherein said first flowchannels have a serpentine course for heat exchange medium flow.
 16. Aheat exchanger of claim 3 , wherein said fins are formed by punchingsheet metal.
 17. A heat exchanger of claim 9 , wherein said fins areformed by punching sheet metal.
 18. A heat exchanger of claim 1 ,wherein at least two of said second flow channels have differentlengths.
 19. A heat exchanger of claim 18 , wherein said plates areshaped as a radial sector of a circle and wherein said plurality ofsecond flow channels have circular arcuate flow paths of differentlengths.
 20. A heat exchanger of claim 19 , further comprising: at leastone passage aperture for the first heat exchange medium located in saidplates in an inner radial location, wherein each of said second flowchannels is of increasing length with increasing distance from saidpassage aperture.
 21. A heat exchanger system comprising: a firstplate-type heat exchanger, said first plate-type heat exchangercomprising: a plurality of stacked plates, with respective adjacentplates forming pairs of plates, the plates of the pairs being joinedtogether to define a plurality of first flow channels therebetween forcarrying a first heat exchange medium; and fins arranged betweenneighboring pairs of said plates, said fins and at least one of saidneighboring pairs of plates forming a plurality of second flow channelsfor carrying a second heat exchange medium; wherein said fins are shapedsuch that the second heat exchange medium has a general flow directionin said second flow channels that is changed as it flows through theheat exchanger; and a second plate-type heat exchanger, wherein saidfirst and second heat exchangers are integrally connected to oneanother.
 22. A heat exchanger system of claim 21 , wherein said secondheat exchanger comprises: a plurality of stacked plates, with respectiveadjacent plates forming pairs of plates, the plates of the pairs beingjoined together to define a plurality of third flow channelstherebetween for carrying a third heat exchange medium; and finsarranged between neighboring pairs of said plates, said fins and atleast one of said neighboring pairs of plates forming a plurality offourth flow channels for carrying a fourth heat exchange medium; whereinsaid fins are shaped such that the fourth heat exchange medium has ageneral flow direction in said fourth flow channels that is changed asit flows through the second heat exchanger.
 23. A heat exchanger systemof claim 22 , wherein in each of said first and second heat exchangers,said second and fourth heat exchange medium is in each case air and saidsecond and fourth flow channels have a curved course for heat exchangemedium flow, and wherein each of said first and second heat exchangersfurther comprises at least one passage aperture for the first and thirdheat exchange medium, respectively, and each of said plurality of secondand fourth flow channels are of increasing length with increasingdistance from said respective passage aperture.
 24. A heat exchangersystem of claim 23 , wherein said first and second heat exchangers areconnected to one another only in the vicinity of said their respectivepassage apertures.
 25. A heating or air conditioning unit comprising: afirst plate-type heat exchanger, said first plate-type heat exchangercomprising: a plurality of stacked plates, with respective adjacentplates forming pairs of plates, the plates of the pairs being joinedtogether to define a plurality of first flow channels therebetween forcarrying a first heat exchange medium; and fins arranged betweenneighboring pairs of said plates, said fins and at least one of saidneighboring pairs of plates forming a plurality of second flow channelsfor carrying a second heat exchange medium; wherein said fins are shapedsuch that the second heat exchange medium has a general flow directionin said second flow channels that is changed as it flows through theheat exchanger.
 26. A heating or air conditioning unit of claim 25 ,further comprising a blower and wherein said first heat exchanger ispositioned downstream of the blower.
 27. A heating or air conditioningunit of claim 26 , wherein said blower comprises a radial blower.
 28. Aheating or air conditioning unit of claim 26 , further comprising: afilter positioned downstream of said blower, and wherein said first heatexchanger is positioned downstream of said filter.
 29. A heating or airconditioning unit of claim 25 , wherein said first heat exchanger is anevaporator, and the heating or air conditioning unit further comprisinga second heat exchanger arranged downstream of said evaporator, whereinsaid second heat exchanger comprises: a plurality of stacked plates,with respective adjacent plates forming pairs of plates, the plates ofthe pairs being joined together to define a plurality of third flowchannels therebetween for carrying a third heat exchange medium; andfins arranged between neighboring pairs of said plates, said fins and atleast one of said neighboring pairs of plates forming a plurality offourth flow channels for carrying a fourth heat exchange medium; whereinsaid fins are shaped such that the fourth heat exchange medium has ageneral flow direction in said fourth flow channels that is changed asit flows through the second heat exchanger.
 30. A heating or airconditioning unit of claim 29 , wherein said second heat exchanger is aheater.
 31. A heating or air conditioning unit of claim 30 , whereineach of said evaporator and said heater further comprises: at least onepassage aperture for the respective first and third heat exchangemedium, wherein each of said second and fourth flow channels is ofincreasing length with increasing distance from said respective passageaperture.
 32. A heating or air conditioning unit of claim 30 , whereinsaid heater can adjust a flow of said third heat exchange medium.
 33. Aheating or air conditioning unit of claim 30 , further comprising abypass positioned downstream of said evaporator for allowing air tobypass said heater.
 34. A heating or air conditioning unit comprising: afirst plate-type heat exchanger; and a second plate-type heat exchanger,wherein each of said first and second plate-type heat exchangerscomprises: a plurality of stacked plates, with respective adjacentplates forming pairs of plates, the plates of the pairs being joinedtogether to define a plurality of first flow channels therebetween forcarrying a first heat exchange medium; and fins arranged betweenneighboring pairs of said plates, said fins and at least one of saidneighboring pairs of plates forming a plurality of second flow channelsfor carrying a second heat exchange medium; wherein said fins are shapedsuch that the second heat exchange medium has a general flow directionin said second flow channels that is changed in a circular arcuate pathas it flows through each respective heat exchanger.
 35. A heating or airconditioning unit of claim 34 , wherein each of said first and secondheat exchangers further comprises: at least one passage aperture for thefirst heat exchange medium, and wherein each of said plurality of secondflow channels is of increasing length with increasing distance from saidpassage aperture.
 36. A heating or air conditioning unit of claim 35 ,wherein said circular arcuate paths of said second flow channels of saidfirst heat exchanger have a first center located in at leastapproximately the same vicinity as a second center of said circulararcuate paths of said second flow channels of said second heatexchanger, and wherein said second heat exchanger is a heater.
 37. Aheating or air conditioning unit of claim 35 , wherein each of saidfirst and second heat exchangers diverts air through approximatelyninety (90) degrees.
 38. A heating or air conditioning unit of claim 37, further comprising an air mixing valve located on downstream of saidfirst heat exchanger to direct at least a portion of air exiting saidfirst heat exchanger to said second heat exchanger.
 39. A heating or airconditioning unit of claim 34 , wherein said first heat exchangerfurther comprises an exit face, and said second heat exchanger comprisesan inflow face, wherein said exit face of said first heat exchanger isaligned approximately parallel to said inflow face of said second heatexchanger.
 40. A heating or air conditioning unit of claim 34 , whereinsaid first and second heat exchangers are integrally connected to oneanother.
 41. A heat exchanger of claim 4 , wherein said angle isapproximately ninety (90) degrees.
 42. A heat exchanger of claim 1 ,further comprising in each pair of plates, a plurality of knobs on eachsaid plate arranged opposite to one another and brazed together toconnect said pair of plates.
 43. A method for assembling a heat exchangeassembly comprised of a first plate-type heat exchanger; and a secondplate-type heat exchanger, wherein each of said first and secondplate-type heat exchangers comprises: a plurality of stacked plates,with respective adjacent plates forming pairs of plates, the plates ofthe pairs being joined together to define a plurality of first flowchannels therebetween for carrying a first heat exchange medium; andfins arranged between neighboring pairs of said plates, said fins and atleast one of said neighboring pairs of plates forming a plurality ofsecond flow channels for carrying a second heat exchange medium, whereinsaid fins are shaped such that the second heat exchange medium has ageneral flow direction in said second flow channels that is changed asit flows through each respective heat exchanger, comprising: assemblinga stack of said plates for said first heat exchanger in alignment withone another and a stack of said plates for said second heat exchanger inalignment with each other, wherein at least some of the plates of saidfirst heat exchanger are connected to corresponding plates of saidsecond heat exchanger; during said stack assembling, interposing saidfins between each neighboring pair of plates for forming said secondflow channels; and brazing each of said pair of plates together on atleast their outer circumference to form said first flow channels andbrazing said fins to adjacent pairs of plates to form said second flowchannels, whereby said first and second heat exchangers are produced ina single assembly operation.